1. Field of Invention
The invention relates to an electrically powered vehicle drive control device and an electrically powered vehicle drive control method.
2. Description of Related Art
There exists a hybrid type vehicle as an electrically powered vehicle with a vehicle drive device. The vehicle drive device transmits a part of the engine torque to an electric generator (electric-generator motor) and the remainder of the engine torque to driving wheels. The vehicle drive device includes a planetary gear unit that serves as a differential rotation unit provided with a sun gear, a ring gear, and a carrier. The carrier is connected to an engine; the ring gear, a drive motor, and driving wheels are connected together; and the sun gear is connected to the electric generator. Rotation output from the ring gear and the drive motor is thus transmitted to the driving wheels to generate a driving force.
In the vehicle drive device, inverters are arranged between the drive motor and a drive-motor control device. The inverters are driven according to a drive signal forwarded from the drive-motor control device in order to receive direct current from a battery, generate currents of U-phase, V-phase, and W-phase and supply currents of the respective phases to the drive motor. Therefore, the inverters comprise, for example, six transistors as switching elements. The respective transistors are united pair by pair to constitute transistor modules (IGBT) of the respective phases. Accordingly, when a drive signal is forwarded to the respective transistors in a predetermined pattern, the transistors are made ON and OFF to generate currents of the respective phases.
A drive-motor rotating speed sensor is used to detect a rotating speed of the drive motor, that is, a drive-motor rotating speed. For example, a drive-motor torque is controlled on the basis of the drive-motor rotating speed.
By the way, with the hybrid type vehicle constructed in the above manner, a forward range, a backward range, a neutral range, and a parking range can be selected by manipulating a shift lever. When the parking range is selected, the driving wheels are locked to maintain the hybrid type vehicle in a stopped state (for example, see JP-A-5-278483).
Therefore, the ring gear is formed integral with a parking gear. When a driver manipulates the shift lever to select the parking range, a parking lock mechanism is actuated and a pawl with a detent, arranged to be able to swing, is caused to engage with the parking gear to lock the parking gear. The driving wheels are thus locked.